[tip: sched/hrtick] hrtimer: Avoid pointless reprogramming in __hrtimer_start_range_ns()

[tip-bot2 for Peter Zijlstra]

The following commit has been merged into the sched/hrtick branch of tip:

Commit-ID:     d19ff16c11db38f3ee179d72751fb9b340174330
Gitweb:        https://git.kernel.org/tip/d19ff16c11db38f3ee179d72751fb9b340174330
Author:        Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate:    Tue, 24 Feb 2026 17:35:37 +01:00
Committer:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Fri, 27 Feb 2026 16:40:04 +01:00

hrtimer: Avoid pointless reprogramming in __hrtimer_start_range_ns()

Much like hrtimer_reprogram(), skip programming if the cpu_base is running
the hrtimer interrupt.

Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Juri Lelli <juri.lelli@xxxxxxxxxx>
Reviewed-by: Thomas Gleixner <tglx@xxxxxxxxxx>
Link: https://patch.msgid.link/20260224163429.069535561@xxxxxxxxxx
---
 kernel/time/hrtimer.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index 860af7a..3088db4 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -1269,6 +1269,14 @@ static int __hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,
 	}
 
 	first = enqueue_hrtimer(timer, new_base, mode);
+
+	/*
+	 * If the hrtimer interrupt is running, then it will reevaluate the
+	 * clock bases and reprogram the clock event device.
+	 */
+	if (new_base->cpu_base->in_hrtirq)
+		return false;
+
 	if (!force_local) {
 		/*
 		 * If the current CPU base is online, then the timer is